Long story about Eeyore, primarily (5)
I believe the answer is:
yearn
'long' is the definition.
(synonyms)
'story about eeyore primarily' is the wordplay.
'story' becomes 'yarn' (synonyms).
'about' indicates putting letters inside.
'primarily' indicates taking the first letters.
The first letter of 'eeyore' is 'e'.
'yarn' going around 'e' is 'YEARN'.
(Other definitions for yearn that I've seen before include "Long - pine" , "Have strong desire" , "wish" , "Curdle" , "Feel desire" .)